


Fangs of a Brother

by Canadian_BuckBeaver



Category: Undertail - Fandom, Undertale (Video Game), underswap
Genre: Alternate Universe - Underswap (Undertale), Biting, Blood, Blood Drinking, Blood and Violence, Character Turned Into Vampire, Forced Relationship, Grillby's Restaurant (Undertale), M/M, POV First Person, POV Third Person, Protective Grillby (Undertale), Rape/Non-con Elements, Sibling Incest, Underswap Muffet (Undertale), Underswap Papyrus (Undertale), Underswap Sans (Undertale), Unrequited Crush, Vampire Bites, Vampires
Language: English
Status: In-Progress
Published: 2019-02-27
Updated: 2019-10-08
Packaged: 2019-11-06 08:47:32
Rating: Mature
Warnings: Graphic Depictions Of Violence, Rape/Non-Con
Chapters: 2
Words: 4,537
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17936600
Author URL: https://archiveofourown.org/users/Canadian_BuckBeaver/pseuds/Canadian_BuckBeaver
Summary: In the act of protecting his brother from a vampire, Papyrus has been bitten and turned.  He hungers for blood and magic, starving and weakening until he receives his meal.  Sans stays with him, guilt of knowing that he was the cause overwhelming him.However, Papyrus' bite has perverted his personality and needs.  He hungers specifically for the blood and marrow of his brother and, as the days drag on until the next reset, he finds that his hunger has changed.  He longs not just for blood and marrow, but for his brother specifically.





	1. Sans/Papyrus

**Author's Note:**

> It will be a little non-con-ny with the biting and marking and the feeding, there might be some blood and gore in there as well. Watch the tags and protect yourself.

“Please Blue, just a small bite…” Stretch pleaded.  He looked absolutely grey in the skull, his eye lights a dim orange.  “That’s all I need. I… I can’t.  I’m so weak.  So hungry.” A shaky hand outstretched towards him, bones clanking as they fought against the instinct to fall to the floor.  “Please.  All I need is a little bit.” 

Despite his best efforts, Blue recoiled away from his brother.  Stars he hated himself when he did that.  He wasn’t helping his brother like that, yet he couldn’t allow himself to get too close to him like this.  He knew too well what would happen if he did. His neck and ribs still bore the scars.  “I’m sorry. I can’t!  You know that I can’t!” Blue told him, tears in his eyes.  He couldn’t help the tears.  He hated seeing his brother like this, weak and hungry, on the verge of dusting.  He looked so sick. His elder brother was fading away before his very eyes and Blue couldn’t help him.  No matter what Stretch said.  The bite was like a band-aid, would only sate him for a little while before he began crying out for more.  Always more.  The hunger drove him.  “I can’t give you anymore.  I’m still weak from last time!  My magic is so low it is affecting my training.  Alphys even mentioned it.”

The hand fell weakly to the ground before being pulled in by its owner.  Stretch stared unseeing at the ground, his eye lights pulsing weakly.  “I… I understand.” he said finally, curling in on himself. “You need your training… to follow your dreams…. to become a Royal Guardsman.  I won’t… I can’t impede on that…”

“Stretch it’s not that,” Blue tried to argue with him, many more tears welling up in his sockets.  “You know that it isn’t like that.  I’ll get you some more marrow and blood from Undyne.  She just had a blood drive.  It’ll be easy for me to sneak in and make off with a few packages.”

Stretch seemed not to hear him.  His bones were clanking.  “It was my own fault that I got bit,” he said.  “You didn’t ask me for help.  I should have trusted in your training instead of running in and ruining everything as I always do.”

Blue flinched, rubbing at his neck at the memory.  A dark forest, unknown creatures hunting in the dark of the Underground.  Poisonous green eyes and glistening fangs, a blur of movement, and his brother’s unearthly scream.  Marrow flowing freely from a puncture on Stretch’s vertebrae.  The memories of that fateful night still haunt his nightmares, and even have started to poison his sleep.  They had been lucky that Stretch had survived the attack but, not without its side effects.

Stretch had been turned.  His incisors were sharp, able to slide through bone and marrow like melted butter.  Blue knew this from experience.

There was another gasping wheeze, drawing Blue’s attention back to the larger monster.  Stretch’s breath hissed between his ribs, his bones turning ever greyer as Blue watched on.  He was truly weak from hunger, there was no mistaking it. A part of Blue wanted to pull down his familiar bandana, offering his neck to his brother, allow him to feed, but the other part of him, the colder, angrier side was refusing. In a way Stretch’s hunger only had Stretch to blame.  He had been refusing to feed on other monsters, saying that it was his mess to deal with, that they shouldn’t be punished for him.  If only he feed on the blood bags that Blue collected for him.

But no, the only creature’s blood that he would feed on was Blue.

And that was more complicated than it sounds.

Blue wasn’t worried about the marrow or magic loss that occurred when Stretch bit him, that wasn’t it at all. Yes, he would admit that it made him weak for a few days afterwards but his levels always returned to normal again. Stretch would return to normal for a few days before the cycle began again.  And, in a way, Blue owed Stretch his life after he had saved him from the forest’s vampire.  Allowing him to feed on him would be the least that he could do in thanks.

No… it was what else occurred that had Blue hesitating. 

When Stretch bit Blue and began to feed, it awoke strange feelings in Blue.  A prickling in his bones, his soul leaping in his chest.  Strange feelings, ones that he was not ready, nor willing, to entertain.  It would seem that the venom in Stretch’s salvia was not only an anticoagulant, allowing blood to flow smoothly, but also a weakened aphrodisiac.

And for his brother to be slipping him this arousal drug, it just felt wrong.  So very wrong.  Incest was not unheard of in monster times, like the humans, there had been a time where Royals would marry their siblings to keep their bloodlines ‘pure’ and untainted.  But, they were not Royals, and incest was long since frowned upon.  Blue loved his brother, but not in that way.  That way was wrong.  He loved him as one was supposed to love their family.

But Stretch didn’t seem to care.  His long limbs would wrap around Blue, pulling him closer as his fingers would slowly explore his body.  His fingers would slip under his battle body and make their way to his ribs or pelvis, stroking the sensitive curves.

Blue shuddered in a mixture of disgust and lingering arousal at the memory. He hated it when feeding time came.

And yet….

He knew that he wasn’t the only one suffering.

His eye lights fell to Stretch, a worried pucker returning to his sockets. Stretch was watching him, silently pleading for him.  Orange eye lights dimming slightly. 

His brother was seriously weak and sick, begging, **begging** , Blue for help.  He had always been so strong, looking after Blue when they were young boys, making sure that there was milk in the fridge and food on the table.  Helping Blue follow his dreams even if he didn’t necessarily agree with them.  And now, now Stretch was the one who needed his help.

And who was Blue to refuse?

“Just… just a small bite… and be careful.” Blue whined softly, pulling down the bandana with shaking hands.  His vertebrae was already scarred with the marks of teeth.  “I don’t…”

It was like he hadn’t spoken.

Hands reached out, pulling Blue into his brother’s lap, orange-clad arms holding him tight against his brother’s chest.  Stretch growled, scenting blood and marrow, the dim orange eye lights turning dark, the orange core igniting with new light.  Before Blue could prepare himself properly, his neck was pulled up and away, fully exposing his vertebrae.  There was a hard, burning puncture as Stretch’s fangs broke the surface of the bone.

After that, darkness burned away his sight, and he fell into Stretch’s embrace.

* * * * *

This timeline is one of the worst timelines that I had experienced.

Timelines were never the same.  There was always something different about them.  Sometimes it was almost unnoticeable in its insignificance, other times it was glaringly obvious. I never knew what would be different.  Nor was I sure what caused these differences between them.  I still felt ashamed at that. After all this time, I wasn’t sure, what caused the little fluctuations in Underswap.  What caused some little, insignificant things to be different and yet the story to remain relatively the same?  The Surface Dwellers would sometimes speak of the Butterfly Effect, how the littlest action had the possibility to have catastrophic consequences.  If I had to guess, I would say that it was the work of a human.  One who was trying to keep things “fresh and interesting”.  Perhaps entertain themselves somehow.

Is this how the God of how those Surface religions feels?  Drunk on the control of his puppet strings?  Overzealous on how to punish those who fall under his reign?  The child thieved on attention so this was entirely possible.

Yet, even as my hatred for the human grew, I knew that not everything could be explained by the human alone.

However, even with these little discrepancies, there was a pattern on how our year would play out.  Every year, on the same day, the human would fall.  Depending on their mercy, the monsters may be freed from their imprisonment, or slaughtered by the human.  Or, in their more “ingenious” runs, the human may try some combination of killing and sparing, just enough to toy with our emotions.  With all sanity.

Like I said, a puppet master drunk on control.  They didn’t care who they hurt and why.  They wanted to play.  That much I understood.  And there was much that I still didn’t.  For a while I was content with that.  It would prevent me from falling down I assumed, something new and interesting every timeline while I waited for death or reset or even both.

And yet, in this timeline, something terribly went wrong.  I should have seen it coming.  I sensed the darkness as it slowly came closer, and yet I did nothing.  Curse my lazy, good-for-nothing personality. I thought it was just a side effect of the last reset. That it too would eventually fade away.  Even as it came closer and closer I did nothing but ignore it.

We had all been told stories of myths and legends, told tales of dragons and knights and far away lands.  Hell, I told the same stories to my brother as we grew up.  It was part of the reason why he had wanted to join the Royal Guards and be trained by Alphys.  Undyne would lend us books and movies and we would read them all day and night, forgetting the hunger in our bellies, the longing for something, or someone else.

But we never expected them to be real.

I couldn’t let the vampire bite Sans.  My brother, my very link to this broken world.  The only one besides my honey that could make me smile.  So I took the bite.  There was one thing that I hadn’t thought of when I stepped in between my brother and this beast.  This was no feeding bite, this was a bite with an intent to change. 

To those who have never been bitten by a vampire, there are no real words to describe the pain, so forgive me for rattling on.  The teeth sliced through my bones easily, but once the vampire completely bit down, the bones cracked, spreading to others.  The saliva that a vampire produces is used to keep blood flowing, much like an overgrown mosquito, but it burns like a motherfucker as it hit hits your system.  So this saliva flowing through the entirety of your body, and air entering parts of your body where it isn’t supposed to and you have a squirming monster, one screaming for the heavens to end their miserable existence.

Luckily for this particular skeleton monster, I passed out.

After the bite, the first thing I remember is Sans next to me, whispering softly as his scarf pressed to my neck.  He’s trying to stop the bleeding, trying to save me.  He’s whispering for me to hang on, that he would do anything if I remained alive.  I remember wanting to chuckle at the thought of Sans turning his back on my little sock mountain in the living room, how he would have to buy honey every day for the rest of our lives to keep me satisfied.  But I was too weak to speak.  I remember thinking that, with his eyes filled with tears, they rivalled the brightest stars on the Surface.  That they were brighter than any jewel.

How I wanted to see them everyday for the rest of my life.

My eyes shut again, leaving Sans’ voice disoriented and blurry.  Fever overtook my body and began to change me.  No longer would I just be a regular skeleton monster, even now I can still make those horrible jokes that Sans’ hates so much.  I would become a creature thirsty for blood and marrow.  I too would become a vampire.  But I was a vampire without a teacher, without one that could show me the ropes.

I was a loose canon in their terms… and I became highly dangerous.

The burn of the bite burned every part of me that remained after the timelines.  Anything good in me withered away and died, leaving me a husk of who I was.  Instead of being carefree, I became obsessive.  I became jealous and controlling.  I needed blood, and I needed my brother.

You see, reader, when someone turns to a vampire, your very essence both dies and magnifies.  Had the vampire been able to change me himself, he would have been able to focus on what he wanted to be changed.  Perhaps my lazy attitude, perhaps amplify my magic.

But no, the vampire had run off after he had bit me, and now I was changing.

My thoughts focused on my brother.  How dear he was too me, how much I loved him.  How I had looked after the both of us after dear old dad left us for whatever scientific journey called his name.  I had raised Sans alone, had been there for everything.  Sans was my brother, my best friend, he was my son in many ways.  We had been there for each other through thick and thin, timeline after timeline, reset after reset.  I loved him dearly.

And that, dear reader, was what was amplified in my changing.

Confused?  Allow me to explain.

With my thoughts on Sans, my warping mind fixated on him.  How he had begged me to stay alive, how he would do anything in his power to keep me there.  How he had wanted me to remain by his side.  My sick, twisted mind focused on him, perverted my thoughts of him.  What were innocent begs of a brother losing a brother became the begs of a lover.  I had looked after Sans for so many years so he was mine, he belonged to me and me alone.  I could hear the sound of blood and marrow flowing through his bones and claimed them as mine.  Only they would be able to sate me.  Sate the terrible hunger that raged within me.

Stars, the hunger.  It consumes every emotion, every thought.  Even now I can feel it building, drowning everything else out.

It will become my undoing. That much I do know.  I will hunt down all blood and marrow until the day I mercifully dust, or until the human resets the timeline.

The next timeline would be different.  I would keep Sans from that neck of the woods, I would protect both himself and I better….

If only to make sure that he belonged to me alone.


	2. Grillby

**Summary for the Chapter:**

> Sans has been missing for a few days and it hasn't gone unnoticed. Grillby misses his little friend and approaches Alphys for help. If only to make sure he is ok.

The war between monsters and humans was a devasting one.  It had dragged on for years, neither side giving an inch.  Humans won some, monsters won others.  In the end, the power of the humans’ soul and their determination proved to be stronger than the collective might of the monsters’ magic.  Eventually they we were overpowered and pushed into defeat, forcing their surrender.  It was after they had been forced to sign the peace treaty that the human’s viciousness, their sadistic nature, truly came to light.  You see, humans wanted to make sure that they and their future generations would know of their glory, of their superiority, and how monsters would forever know their place.  Monsters were weaker than humans, not deserving of their respect.

They were beneath the humans.  They no longer had the same rights or recognitions.  So why would humankind be forced to stare down upon their lesser, why should their lesser have access to the same limited resources that they, the victors, did?  It made no sense to the generals. Why share when one can have everything?

So, combining the last of their magic, they drove the monsters to Mt. Ebott, sealing them away.  No longer would they be forced to view them, forced to share or live with them.  They could enjoy the spoils of war and live in peace, knowing that somewhere underfoot monsters toiled and rotted away. 

When the humans sealed the monsters away, they did their best to seal them away from anything that would give them any sense of comfort, of familiarity.  The Surface belonged to the humans, only they were entitled to the passing of time, of the sun and the moon, of the weather and seasons.  Not even weather was something that wasn’t supposed to happen in the Underground. 

However, we all know that the last laugh was on the humans themselves.  Monsters had defied all speculations.  They had survived, no thrived, under the barrier, far from the sun and fresh air where they once lived.  Their stories may have faded, as did the evidence of the monsters existence.  Those who once grew up with monsters, or fought across from them, slowly became fewer and fewer.  Stories faded, their legends died.  Admiration soon made way for speculation.

Monsters were a thing of fantasy for the humans.  Those who swore to have seen one were quickly dismissed as crazy.

But this was not a new story.  Every monster knew this story, told from the time that they were young, until the time they dusted, Grillby thought to himself as he looked out the windows of his café.  It was a cold night, cold even for late December.  He idly polished one of his many glasses as he stared out the windows, his pupil-less eyes following the snowflakes as they danced and wove through the night.  It was one of those nights where cold, wet snow and sleet pounded against the windows, the wind screaming around the corner.  It was a disgusting night outside, hell, probably one of the worst snowstorms that the Underground had had in over a century of living under the Surface. 

At least amongst the small roar of the crowd inside, the sounds of outside couldn’t be heard.  Monsters of all shapes and sizes sat around, drinking Grillby’s speciality drinks or coffee, talking to one another.  The flaming bartender looked around at the crowd as he set down the first glass and began to polish another glass.  He nodded to himself, finalizing an inner argument that he had been having with himself.  Even though the outside was miserable, the shop was warm and cozy. This was just how Grillby liked it.  It reminded him on how Christmases used to be with his family.  Everyone coming together, chattering to one another and catching up.  Friends meeting together and making more friends, families enjoying their time together.  It felt welcoming, like everyone belonged inside.

Well.  Almost how he liked it.  If he was truly being honest with himself, he knew that there were two important friends missing tonight.  Again.  Instinctively his eyes flickered to two empty stools that were across from him, causing him to frown.  Another night without them here.  It had been months since he had seen his two favourite customers.  Although he knew that Papyrus and Muffet had some sort of complicated relationship, that didn’t explain where Sans was.  The little skeleton had once mad it habit to come into his bar after training for a little pick-me-up, usually one of Grillby’s milkshakes or even the less popular protein shakes.  If he was allowed, Sans would sit and talk for hours on just about anything.  Training, humans, puzzles, cooking, the list seemed limitless.  But now there was no cheerful voice or large smile, no twinkling eye lights poking over the rim of a class.  It caused a little pang in Grillby’s soul.  Of course he didn’t realize until now just how much he had looked forward to seeing him.

The chatter continued and Grillby began to listen in to some of the conversations without being overly obvious.  Tonight he was hoping that he could overhear someone talking about the skeleton brothers.  Being a bartender was funny in a way.  The monsters seemed to forget that Grillby was a ‘normal’ monster, one that was capable of overhearing and understanding their conversations.  Monsters would continue their discussions even if he was standing beside them or in front of them.  Though he would admit that a majority of their talk was rather tame and mundane, normal things that you would talk about in public – the weather was gross and had no sign of stopping anytime soon, the king was still refusing to talk to the queen, the state of everyone’s gardens, etc. – though he would admit that he had heard his fair share of spicy and gossip worthy items.  Tonight he had no luck though.  Seemed as if the snow and weather was on everyone’s minds.

Taking a quick glance around, he couldn’t help but notice that Alphys wasn’t socializing with the rest of the monsters.  She was all alone for once.  Usually she would be with Undyne or with the rest of the Royal Guard members, but not tonight.  Undyne hadn’t shown up tonight it seemed, and the dogs were gathered around the fireplace, yapping to one another excitedly, filling the bar with the faint scent of wet dog.  Tonight, Alphys was sitting in one of the open booths, a book open as she sipped on her drink.  He could even see that there was a faint flush on her cheeks as she flipped the page.  It was probably one of those spicy human books that Undyne had found at the dump for her.

Now, normally Grillby wouldn’t ever dream of approaching the Captain of the Royal Guards in such a position.  Alphys was the toughest monster in all of UnderSwap, other than that of the Queen herself.  Her body was riddled with body scars and muscle, her Warhammer by her side as always.  Here she was in his bar, obviously looking to be alone, trying to enjoy her book and drink in peace while keeping an eye on everyone and their own shenanigans.  It was not an opportunity that one weak of heart or soul would, or should, take lightly.  Yet it was the perfect opportunity to get whatever information that he could out of her.  He was worried about the skeleton brothers, in particular Sans.  It simply was unlike Sans to be gone for so long.

Or to remain so quiet…

 * * * * *

_“Please.  Do not leave me,” Chole begged, staring up into Isabelle’s ice blue eyes.  Those olive eyes danced with tears, begging her to understand, to hear her.  The blue eyes stared down at her in shock and surprise.  “Please.  I… I know that I have asked for so much already.  But please, do not leave me tonight.  I cannot bear to be alone.” Chole stepped close to Isabelle, her hands tracing her hips and slowly pulling herself close.  Isabelle could see every shimmer of the tears that beaded on her eyelashes.  “Please… stay with me? Will you share my bed tonight?”_

_Isabelle reached out, fingers brushing a few strands of hair away from Chole’s face.  The once impeccable make up had all but melted away into nothing.  Despite where they stood, Chole grasped her hand, leaning into the touches.  Silently begging her with her body.  The strong, capable woman was gone and, in her place was someone that was vulnerable.  Someone that needed her. Someone that could lo-_

“My apologies for interrupting your reading, Captain.”

Alphys gave a very uncaptain-like shriek and slammed the book shut, turning to face the owner of the noise.  Grillby stood there, a couple paces back, and just out of reach of swinging arms.  Alphys took a shuddering breath, feeling her soul stagger in her chest.  “Grillby.  I swear to Toriel you gave me a fright and a half.”

There was a soft chuckle from the bartender as he placed the refilled glass in front of her.  “Believe me, it was not my intentions.  I apologize, Captain Alphys.”

Alphys’ attention had already changed from him to her book.  She had unfortunately slammed the book shut without placing her page stopper in.  Now she would have to find where she left off before she could continue.  “It’s fine.  Just don’t tell anyone else that you managed to sneak up on me or I might find myself out of a job.”  She began to flick through the pages again, but paused when she still felt his presence.  He did not move from his position.  Instead, he stood there as if she had said nothing at all, tray being slowly wrung in his hands.  “Do you have something else that you wanted to ask me, or did you simply wish to try your luck at scaring the shit out of me again?” she finally said, an edge to her voice.  She knew that she wouldn’t get any peace or be able to read until she was alone again.

The bartender looked almost a bit awkward.  If a flame monster could sweat, he was definitely doing it. “I’m sorry for bothering you.  I just had a quick question for you.”

“I’m all ears.” Alphys begrudgingly put her book down.  She would look for the page once he was gone.  Then she could have some much needed time alone and space to read. 

Knowing her luck, all it would end in is more monsters coming up to talk to her.

The bartender rubbed at the back of the neck.  “You see… it’s about Sans…”

Ah.  Now she understood.  Instantly the hard glint left her eyes, her voice grew soft.  “You’re worried about him, too?” she asked him.

Grillby nodded.  “I haven’t seen him or his brother in more than a few weeks. It’s not normal for them to be so quiet and withdrawn.  I mean, usually you hear Sans coming from miles away, and Papyrus, well he’s usually seen around at his other jobs. But no one has seen or heard from any of them.  And you, with you training him, I thought… well.”

Alphys sighed.  This was going to be difficult to explain.  “Look.  I haven’t seen much of the skeletons either.  Sans hasn’t even been popping up for his training.”

She saw Grillby blink in surprise.  “But… that’s so unusual.  He spent so long begging for lessons and throwing himself into them.”

“Yes.  That’s why I checked on them.  Sans and Papyrus seem to have holed up in their home.  I’m not sure exactly what is going on but Papyrus seems to be sick, Sans looking after him.  All I can say is give him time and he will make a reappearance.  That’s the best I can offer.”

She was about to say more when the door blew open, slamming against the door as the wind caught it.  The bell helpfully rang, signally someone’s arrival.  Alphys and Grillby turned towards the sound.  “Well.  What do you know.  It is true what the humans say.  Speak of the devil, or whisper in one’s ear, and they shall appear.”

Blue stood in the doorway, the door slowly being shut behind him.


End file.
